I've been recently thinking about instanced dungeons, whereby each player has their own private copy of the location in which they can play. In particular, I've been considering how the concept of instancing runs counter to the idea of a multi-player virtual world.

A traditional single-player game is fully instanced. You might be able to upload a high score, to see how you did compared to other players, but you won't be able to interact with other players during the game.

In many modern games, such as Diablo 2, you generally play alone in your own instanced world, although you can also invite other players to play with you. In some games, such as CounterStrike, there is little reason to play unless other players have joined your instance.

In Guild Wars you can meet other players in the safe zones, but all of the fighting takes place in your own instanced world, although you can invite other players to join you.

In World of Warcraft you can encounter people while wandering through the land, but the game also makes extensive use of instanced dungeon areas.

In EVE Online there is no instancing at all.

How much instancing can you include before your game is no longer a multi-player virtual world? Which of the above would you consider (or not consider) multi-player virtual worlds, and why?

Is it possible to have a mud which isn't a multi-player virtual world?

I haven't used any instancing, but In college I briefly (for a day) ran a mud that was not entirely virtual: there were items that could be transferred between the game world and the real world. There was a box near a cluster of computers in the dorm which contained a bunch of numbered items, and if, in the game, you found one of them then you could take it out of the box. There were more numbered items hidden about the campus and if you found one of them, you could transfer it into the game by typing in the number. It was a puzzle-oriented Hitchhiker's Guide to the Galaxy-themed game, so you had a technological gizmo in-game used to effect the transfers.

Instancing doesn't, in my mind, prevent the manifestation of a multiplayer game (talk about $5 words for a 5 cent idea). I'd base it more on the number of interactions expected/required/observed between players. To give an idea, although Guild Wars provides instancing all over, it is primarily a pk game with a heavy emphasis on team-play (4v4, 8v8, 8v8v8v8v8v8, etc). On the hand, some Nethack servers allow players to talk to each other, but it is still a single-player game (even if they might be able to observe one another and communicate, they can't interact outside of words - similar to running IRC while you play).

Personally, I *love* the instanced approach used in Guild Wars (so much so that I've adopted it in the server I work on as a hobby).

The reason I like it is because I can spend my online time (which is a precious resource) with like minded people who I've come to know and trust, while minimizing my exposure to those who are just out to make trouble. The quality of my online time is enhanced by being able to choose who I spend it with.

To me, this is still a virtual world because I can meet and chat with anybody in the "common" areas, but then choose those I want to group with in the "quest" areas.

I think it depends on the game design philosophy. Instancing is great for casual and "fun" players who want an enjoyable game and don't want to have to worry about resource availibility, undesirables, etc. OTOH, it is less of an open multiplayer environment. In a true open environment, players must deal with such challenges and potential threats. Which appeals much more to the "hardcore" players such as PKers and many Socializers, but is less appealing to the masses.